1. Field of the Invention
This invention relates generally to power supplies and, more particularly, to an MOS power supply for generating a regulated negative output.
2. Description of the Prior Art
Typically, to create a regulated negative supply from an unregulated source, one would use a zener diode and a unity gain buffer and employ a voltage divider at its input or output. The problem with such an arrangement is that the reference voltage generated V.sub.REF would be proportional to V.sub.DD -V.sub.Z where V.sub.Z is the voltage across the zener diode. Therefore, the output of the voltage regulator would vary as V.sub.DD varies. If V.sub.DD were to increase, the negative supply would tend to decrease in magnitude. As V.sub.DD decreases, the negative supply would tend to increase in magnitude.
Other disadvantages reside in the necessity for external capacitors. This means that certain package pins must be dedicated to connecting the external capacitors to the remainder of the integrated circuit.